The pharynx is a structure that connects the digestive and respiratory tracts. It makes up the part of the throat situated immediately posterior to the nasal cavity, posterior to the mouth and superior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx, the oropharynx and the laryngopharynx. The proper functioning of pharynx and its neighboring structures within the larynx, base of tongue, soft palate and upper esophagus, ensures that the bolus is transported correctly from the mouth into the esophagus without entering the airway and that the air is breathed in and out free of the digestive tract.
The proper functioning of the pharyngeal and laryngeal reflexes is crucial for swallowing and breathing to work without interference between them. The laryngeal adductor reflex, swallowing reflex and cough reflex are major reflexes involved in regulating these processes. The laryngeal adductor reflex, which involves the adduction of the vocal cords, is triggered by mechanical and chemical stimuli of the pharyngeal-laryngeal mucosa and protects against the entry of food and foreign material into the lower respiratory tract. The swallowing reflex is triggered by mechanical and chemical stimuli in the lining of the base of the tongue and pharynx, and generates synchronous contraction or relaxation of different muscle groups of the tongue, soft palate, pharynx, larynx and esophagus for food to pass quickly from the mouth into the esophagus without entering the airway. If food or liquid enters the airway, it may enter the lungs and allow harmful bacteria to grow, resulting in a lung infection called aspiration pneumonia. The cough reflex serves as protection against possible failures in the above reflex mechanisms where food has been allowed entry into the airway. The cough reflex is triggered by mechanical or chemical stimuli on the laryngeal or tracheal mucosa and allows the removal of the material that has entered the airway.
To establish the parameters of swallowing disorder, it is useful to perform examinations of these reflexes. For example, Aviv et al. introduced an apparatus and procedure to clinically examine the sensory thresholds of the laryngeal adductor reflex by air pulses, as described in U.S. Pat. No. 5,970,978, the disclosure of which is incorporated by reference herein in its entirety. This testing of Aviv was known as “Fiberoptic Endoscopic Evaluation of Swallowing with Sensory Testing (FEES-ST).”
In concordance studies, it has been observed that intra-observer reproducibility of the FEES-ST reflex testing is good in experienced operators of the apparatus, but poor in inexperienced hands. The inter-observer reproducibility is poor both between experienced observers and inexperienced observers. Tests performed by experienced observers regarding the sensation threshold changes in pharyngeal and laryngeal reflexes can be useful to predict outcomes, such as penetration, aspiration, and pneumonia. However, good predictions cannot always be made due to unreliable reproducibility of the tests.
It is noted by the current inventors that the problems that compromise the reproducibility of the FEES-ST sensory test may be related to factors that induce variation in the pressure of air pulses over the laryngeal mucosa. Further, the pressure of air pulses over the laryngeal mucosa may vary considerably due to (often unnoticed) changes in the distance from the tip of the endoscope to the site of impact as well as the angle at which the pulses of air strike the mucosa. The air pulses can easily change during the exploration of the reflex, particularly by inexperienced observers, due to patient movement as a result of discomfort or due to difficulties or personal differences in the estimate of the distance or angle of impact. Furthermore, the variations in the actual air pulses delivered to the mucosa could be due to the variability in the air supply sources, such as compressors of different specifications and air channels or tubes of the endoscope for delivering the air pulses which may have different length, material, and/or diameters.
There is a need for an improved design for the apparatus to make sensory thresholds measurements more precise to improve the intra and inter-observer reproducibility and to allow for more reliable diagnosis of patient conditions relating to the airway or digestive tract.